1. Field of the Invention
The present invention relates to a new and improved light-modifying apparatus for use with light exposure devices such as copiers, contact printers and the like, etc. used in the graphic arts industries. Oftentimes, it is desirable to change the character of the light passing through an image sheet toward a light sensitive copy sheet. For example, collimated light may be changed to diffused light so that "spreads" and "chokes" may be used to provide small dimensional changes of characters on an image sheet. Prints reproduced with diffused light may vary considerably from prints made with ordinary collimated light and, in addition, the present invention is useful to provide a filtering action for filtering out an unwanted portion of the spectrum of light or for attenuating light energy in certain wavelengths when using particular types of light sensitive copy sheets or image sheets of either a positive or a negative type.
2. Background of the Prior Art
One of the problems associated with exposure devices is the problem caused by dust and other particles often present on image sheets, copy sheets and rigid transparent sheet materials used in such exposure devices. Such accumulations of dust and other particles cause "pinholes" to be present in a printed copy and for this reason, diffused light rather than collimated light is often desired to minimize the presence of such pin-holes. It is also desirable to provide a sheet of light diffusing media spaced between the source of light and a positive or negative image sheet and a light sensitive copy sheet which are contained between a rigid, transparent sheet of glass or plastic material and a vacuum blanket for holding the sheets in precise registration. A wide variety of flexible plastic films have been developed for modifying the character of light energy including drafting films made of plastic resins sold under the trade name "Mylar" which may have a frosted surface on one face for diffusing the light and thereby enabling techniques such as "spreads" and "chokes" to be practiced for changing the dimensional characters of the images that are reproduced. It is also desirable to provide a flexible film for a light filter positioned between the light source and light sensitive copy and image forming sheets so that the colors reproduced may be modified or changed from a wide spectrum to a relatively small spectrum of the wavelength of available light energy.
Yet another need encountered in exposure devices of the character described is to provide an attenuating filter of film media positioned between a light source and a light sensitive copy and image sheets which is able to hold back a certain amount of the light otherwise present for producing a precision controlled exposure of the light sensitive medium.